The field of the present invention relates to optically encoded labels and label systems. In particular, spectrally-encoded labels and label systems are disclosed herein.
The identification of objects via mechanical, electronic, and optical means rather than direct visual inspection is an important function. The familiar spatial bar codes that are imprinted on many packaged products, for example, allow opto-mechanical-electronic readers/scanners to identify products while rapidly forwarding identification information to inventory computers or other record keeping devices. Bar codes are typically read by a spatially scanning laser beam which passes successively across a series of lines of various thicknesses. An optical detector receptive to light scattered or transmitted by the label sees a series of temporal changes in the light level and acts to convert the temporally varying optical signal to an electronic facsimile comprising temporally modulated voltage or current. Identification information is extracted electronically from the temporally structured electronic signal.
In order for a spatial bar coding system to function, it is necessary that the scanning optical beam, typically a laser beam, be of a suitably small diameter where it strikes the bar code so as to be capable of serially illuminating the label's constituent spatial elements. If the beam diameter is too large, the temporal structure of the scattered or transmitted optical signal will be washed out. The more distant a label is relative to a scanning device, the more difficult it becomes to ensure that the scanning optical beam will have a sufficiently small diameter to adequately resolve spatial structure encoded on the label.